Many types of electro-optical phototubes are regularly used for detecting a quantity of light passing through a transparent guide medium such as a light pipe. These phototubes typically have a flat, smooth transparent window through which light to be detected is received. To allow proper conduction of the light from the transparent material to the window of the receiving tube, the surface of the transparent material is usually ground and polished so that it is flat and smooth. The flat surface of material is then bonded to the window of the phototube.
The bond between the phototube and the transparent material is formed with with an epoxy which is strong enough to hold the two surfaces together, but which is transparent to the wavelengths of light which are to be detected with the phototube. Such a bonded connection typically provides good transmission of light between the transparent material and the phototube. However, no simple way of decoupling the phototube from the material exists. If for some reason it becomes desirable to decouple the phototube from the transparent material, the bond between the two surfaces must be severed. This requires that the epoxy joint be mechanically broken. The breaking process is inherently violent and often leads to the destruction of the phototube or the transparent material, or both.
In addition to the possibility of destroying the components of the connection, it is also usually difficult to replace the tubes due to the environment of their installation. Very often, the phototubes are installed in devices or machinery in which space is limited. In such an application, it is usually difficult if not impossible to position a temporary fixture to properly hold a phototube while it is being epoxied to the transparent material. Also, the epoxy used to connect a new phototube to the transparent material is usually abundant, and tends to seep onto other elements of the device in which the phototube is to be installed.